Gasless ignition composition for solid rocket propellants



United States Patent 3,140,208 GASLESS IGNITION COMPOSITION FOR SOLIDROCKET PROPELLANTS Barnet R. Adelman, Atherton, Califi, assignor, bymesne assignments, to the United States of America as represented by theSecretary of the Army N0 Drawing. Filed Jan. 18, 1962, Ser. No. 167,1934 Claims. (Cl. 149-41) This invention relates to a gasless ignitioncharge for solid rocket propellants made entirely of noncriticalinexpensive materials.

Prior to this invention difliculty and non-uniformity resulted in theignition of rocket propellant igniters. Igniters of the. prior art werecharacterized by erratic ignition over wide temperature ranges (from 100F. to 200 F.) so that under-ignition resulted at low temperatures andhigh pressures while over-ignition occurred at high temperatures.

The primary object of the present invention is to produce a uniformlyburning gasless propellant igniter.

Another object of this invention is to produce an igniter which willsatisfactorily operate in a temperature range from '100 F. up to 200 F.

Other and further objects and advantages will become apparent to thoseskilled in the art from the following examples and disclosure.

I have discovered novel gasless igniter compositions which areadvantageously employed for the ignition of solid rocket propellants.Ignition is accomplished by a conventional electric squib or match whichignites the igniter composition, which in turn ignites the larger solidpropellant charge. Location of the igniter is generally at the head endof the grain, but may be at the nozzle end of the grain in the case ofend-burning grains. The beneficial advantages displayed by this ignitercomposition arise from the ignition and combustion of the propellantsurface rather than the igniter itself, to provide the gas necessary tocreate the initial pressure in the chamber.

The igniter powder is made by tumbling the powdered metallic fuel withthe granular inorganic oxidizing salts in a sweetie barrel in an inertatmosphere and under carefully controlled conditions to prevent staticdischarges. The composition may be used in either the original powderedform or a tablet form which is made in a conventional tableting pressusing the powder alone or the powder mixed with an amount (usually notmore than about 3 percent by weight) of an organic binder materialsuflicient to agglomerate the ingredients. Examples of suitable bindersare cellulose acetate or ethyl cellulose.

The particular novelty of the present invention resides in the largeamount of iron used for metallic fuel. Iron powder displays greaterradiant energy output over the entire spectural range than any othermetal. While pow- 3,140,208 Patented July 7, 1964 "ice dered iron is themajor component of the present composition, minor amounts of variousother metals may be supplementally added in amounts up to about 5percent by weight to produce desired performance characteristics in theigniter. Magnesium, aluminum, cobalt, boron, zirconium, nickel-zirconiumalloys, iron chromium, and mixtures thereof exemplify the type ofsupplemental metal powders which may be employed in this composition.Alkali and alkali metal nitrates and perchlorates furnish a source ofoxygen for the metallic fuel so that high temperature combustion willproduce hot particles of metallic oxides which form ignition sources onthe propellant surface. Stoichiometric proportions or over-oxidizedproportions, i.e., an oxygen balance a little over the Stoichiometricpoint, produce the most efficient igniters.

The following is a table illustrating a few of the practical embodimentsof the present invention.

A black powder booster may be added to the above compositions in varyingamounts up to 5 percent by weight, depending on the power of the squibused. With a powerful squib the black powder may be eliminated.

It is to be understood that various modifications and extensions may beeffected without departing from the scope and novel concept of thepresent invention.

I claim:

1. An igniter composition for a solid rocket propellant consistingessentially of powdered iron of a major amount by weight and potassiumperchlorate.

2. An igniter composition in accordance with claim 1 including a smallamount of a supplemental metal.

3. An igniter composition in accordance with claim 1 including up to 5%of black powder.

4. An igniter composition in accordance with claim 1 including anorganic binder in an amount sufficient to agglomerate the powdered ironand salt.

References Cited in the file of this patent UNITED STATES PATENTS763,665 Hall June 28, 1904 1,613,120 ONeal et al. Jan. 4, 1927 2,988,876Walden June 20, 1961 3,025,795" Sutton et al Mar. 20, 1962 FOREIGNPATENTS 11,073 Great Britain July 11, 1893

1. AN IGNITER COMPOSITION FOR A SOLID ROCKET PROPELLANT CONSISTINGESSENTIALLY OF POWDERED IRON OF A MAJOR AMOUNT BY WEIGHT AND POTASSIUMPERCHLORATE.